/
env.go
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/
env.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package config
import (
"fmt"
"os"
"strings"
)
type envConfigProvider struct {
prefix string
provider EnvironmentValueProvider
}
const defaultEnvPrefix = "CONFIG"
// An EnvironmentValueProvider provides configuration from your environment
type EnvironmentValueProvider interface {
Get(key string) (string, bool)
}
var _ Provider = &envConfigProvider{}
// foo.bar -> [prefix]__foo__bar
func toEnvString(prefix string, key string) string {
newKey := strings.Replace(key, ".", "__", -1)
if prefix == "" {
return newKey
}
return fmt.Sprintf("%s__%s", prefix, newKey)
}
// NewEnvProvider creates a configuration provider backed by an environment
func NewEnvProvider(prefix string, provider EnvironmentValueProvider) Provider {
e := envConfigProvider{
prefix: prefix,
provider: provider,
}
if provider == nil {
e.provider = osEnvironmentProvider{}
}
return e
}
func (p envConfigProvider) Name() string {
return "env"
}
func (p envConfigProvider) Get(key string) Value {
env := toEnvString(p.prefix, key)
var cv Value
value, found := p.provider.Get(env)
cv = NewValue(p, key, value, found, String, nil)
return cv
}
func (p envConfigProvider) Scope(prefix string) Provider {
return NewScopedProvider(prefix, p)
}
func (p envConfigProvider) RegisterChangeCallback(key string, callback ChangeCallback) error {
// Environments don't receive callback events
return nil
}
func (p envConfigProvider) UnregisterChangeCallback(token string) error {
// Nothing to Unregister
return nil
}
type osEnvironmentProvider struct{}
func (p osEnvironmentProvider) Get(key string) (string, bool) {
return os.LookupEnv(key)
}
type mapEnvironmentProvider struct {
values map[string]string
}
func (p mapEnvironmentProvider) Get(key string) (string, bool) {
val, ok := p.values[key]
return val, ok
}